U.S. Pat. No. 5,952,110 discloses a layer system in which coarse particles are present in an outer layer. The coarse particles project out of the outer surface and serve to increase the abrasive resistance. The coarse particles have a different chemical composition than the layer.
U.S. Pat. No. 5,579,534 discloses a layer system which includes at least three layers and in which coarse particles are arranged on a layer of finer particles.
U.S. Pat. No. 6,444,331 shows a bonding layer which has been roughened in order to achieve improved bonding of thermal barrier coating and bonding layer.
However, layer systems still suffer from poor bonding of the layers to one another or of the layer to a substrate.